A magnetostrictive pressure sensor is a sensor that utilizes an inverse magnetostrictive effect in which a magnetization direction of a magnetostrictive material changes due to distortion of the magnetostrictive material. Patent Literature 1 discloses a device provided with a bottom portion connected to a cylinder of an engine, an upper portion that functions as a cover, and a channel that extends through the bottom portion and the upper portion and receives an inflow of gas in the cylinder. An end portion of the channel on an opposite side to a gas entrance side thereof is closed, and a tube is provided in the channel. A wall portion of the tube becomes deformed under a pressure inside the tube. Furthermore, such deformation of the tube is transmitted to a measurement unit provided in the bottom portion via a first measurement body provided in the bottom portion so as to be in contact with the tube and a second measurement body also provided in the bottom portion so as to be in contact with the tube. The measurement unit is formed of a magnetoelastic sensor, a distortion gauge sensor, a piezoelectric sensor, or the like.